Automatic trim control for



Dec. 19, 1939i B. e. CARLSON 2,183,932

AUTOMATIC TRIM CONTROL FOR AIRCRAFT 3 Sheets-Sheet 1 Original Filed May 29, 1937 INVENTOR 55ft G .O'arlsam Dec. 19, 1939. G CARLSON 2,183,932

AUTOMATIC TRIM CONTROL FOR AIRCRAFT Original Filed May 29, 1957 I s Sheets-Sheet 2 ll'nmim 42 8 INVENTOR Dec. 19, 1939.

B. G. cARLsoN' AUTOMATIC TRIM CONTROL FOR AIRCRAFT Z'SBeetS-Sheet 5 w T R X: w

H n u C M; Hm y. M I

,. Patentedbec. 19,1939 I 2 1 3 932 UNITED STATES PATENT OFFICE Bert G. Carlson, Freeport, N. Y., assignor to Sperry Gyroscope Company, Inc., Brooklyn, N.,Y., a corporation of New York Application May 29, 1937. Serial No. 145,419

aenewea October 29, 1938 7Claims. (01. 244-15) This invention relates to the efllcient operation a control valve arrangement 8, which may be of the control surfaces of aircraft, such as the in the form of a multiple pulley block having an elevator, ailerons or rudder, and more particu upper :pulley 9 rotatably mounted in afork ||I larly, to'the improved type of control surface on a'verticaliy slidable stem secured to a which employs a trim tab or other Flettner arpiston l2 in hydraulic cylinder ii. The two outer. 5

rangement. The invention has especial applipulleys l4 and I5 are shown as rigidly secured to cation to the control of the elevating plane, in the cylinder l3 through suitable brackets l6 and which improper adjustment causes loss of flying I6 and cross bars l'l. Preferably, the lower por- Speed and continuous strain on the intercontion of the central pulley is resiliently held below 10 nections between the main control surface and the upper portion of the pulleys l4 and I5 as by 10 the actuating device, whether manual or the e s o o p g l8 Within the y e thus servo motor of an automatic pilot. ordinarily maintaining a curve or slack in the According to my invention, means are provided cables 6 and 1. In case, however, of acontinuwhich are responsive to unequal strain in said ing tension in a cable of predetermined magni- 5 interconnecting members for automatically turntude, the piston 12 connected to that cablewill l6 ing the trim tab until the strain is equalized or be movedupwardly against the spring. eliminated. The cylinder is shown as having a pair of cir- Another featureof my invention isanimprovecular recesses |9,and IS in the inner walls ment in hydraulic servo motors for actuating the thereof, the for e be g co t d to P p 20 trim tab or other control surface on airplanes, leading to one side of the rotary servo motor 2|,

and in which a large overall movement may be and the other pipe 22 leading to the other side ofobtained without the use of long cylinders. the servo motor. Thepiston is likewise provided Referring to the drawings, showing one form with a pair of annular grooves 23 and 23', the

my invention may assume: former connected with a port in communication 25 Fig. 1 is a diagram illustrating the general with pipe 24, connected to the pressure pump 25, layout of'my invention. and the latter with pipe 26 which leads back to Fig. 2 is a face view of the knob for controlling the sump 21. A bypass channel 60 is shown conthe speed of actuation of the trim tab motor. nestin the W nds f h yl l to bypass Fig. 3 is a vertical section of the same. oil or air around the piston when it moves. With 30 Fig. 4 is a vertical section of one of the strain e P st n in h p it n h w in all 3 responsive members or valves which control the ports are closed and the servo motor idle. In hydraulic trim tab motor. case, however, the piston I2 ofthe members 8 Fig. 5 is a vertical section of the preferred form is moved upwardly by the tension of the wire, the of trimtab motor. pump pressure passes from pipe 24 to pipe 20 Fig. 6 is an enlarged sectional detail of an through the communicating ports l9 and 23, and

overflow valve for the crankcase. at the same time a return connection is provided Fig. 7 is a front view, partly in section, of the to the sump through ports l9 and 23 and motor. through pipes 22 and 26. From the connections Fig. 8 is a vertical section of the same, taken shown in Fig. 1, it will be apparent that the approximately on line 8-8 of Fig. 5. control members 8 and 8' are reversely' connected In Fig. 1, one of the main control surfaces or to the servo motor 2| so as to drive the same in rudders, such as the elevator, is shown as of the opposite directions, so that when the tension in articulated or trim tab type having a main surcable 6 is materially greater than in l, the servo face or service rudder I pivoted at 2 to the tail motor 2| is driven in a direction to turn the tab of the craft and a trim tab or auxiliary rudder 3 to equalize such pressure, i. e., to reduce the pivoted on the main surface at 4. The main surpressure in 6 and increase it in l, and vice versa. face may be ordinarily controlled by any suitable Preferably, there is interposed in the pipe line device, such as by the operating lever 5 or from 24 between the pump 25 and the control members the servo motor of an automatic pilot (not a regulating valve 28 to regulate the rate of flow shown), or both, there being connecting cables in the oil system and, hence, the trim tab speed. 50 6 and 1 connecting the actuating device and the This is shown as in the form of a needle valve 29, control surface proper. The trim tab is shown the stem of which is threaded in the valve hous-. as adjusted eithermanually from control meming 30. Preferably an indicator is provided= to ber 5' or automatically from servo motor 2|. indicate the speed of flow set, this being, shown Threaded on each of said cables 6 and I, I-show as a graduated dial 3| rotatably mounted on pin 55 u and having teeth 33 ensasins small teeth on thestemil. Bytheuseofsomesuch timelag device, motor II is made responsive only to continued unbalanced pressure or pull of the service rudder on the control means 5 therefor.

The servo motor is shown as in the form of a multi-cylinder rotary hydraulic engine, the cylinder block 34 being rotatably mounted in anti-friction bearings 35, 35' within the stationary housing 36. Said housing has two pairs of inwardly facing substantially semicircular ports or grooves 31, 31' and 38, 38'. The tops of the cylinder blocks each have a plurality of small ports 62, 62' bored therethrough on both sides in line with ports 31, 38, 31' and 38'. The diametrically opposite pistons l8 are placed apart and the piston rods ll all engage .the common stationary crank shaft 63 which is placed of! center with respect to the bearings 35, 35' and the rotary extension 84 of the housing which drives the pulleys 65 through universal coupling 86. A cable 61 is shown as connecting said pulley with a second pulley 68 concentric with axis 2, from which another cable 68 leads to the trim tab 3. Port 38 is normally connected to one pipe 20 and the other port 38' to pipe 22. Said pipes are shown as entering the engine from opposite sides in Fig. 7, the pipes leading into short radial channels 39, one of which is connected to 38 and engine, which pressure is maintained equal on both sides of the cylinder block. Each of said channels 38, 38 is also in communication with a bypass channel 40 through cross ports 44 and 44', which channel is normally closed by rotary valve 43, but which may be opened by rotating the attached pulley 42 to place the transverse port, through the valve stem 43, in line with the passage 40. The pulley may be manually controlled from a distance through a wire 45 and handwheel 46.

Each passage 39 is also shown as having a normally closed connection 50 to a chamber 5| in communication with the crank case of the engine. The passage 58 is shown as normally closed by a spring pressed ball 52, but in case the pressure in the crank case builds up beyond that in the return side of the line, the ball is lifted from its seat and the oil flows back into the sump. Such a relief valve is employed in each passage so that one valve will always remainoperative regardless of the direction in which the engine is being run.

A safety bypass arrangement is also provided so that the servo motor may be over-controlled manually if desired or necessary. This is shown as in the form of a cylinder 41 in communication with both of channels 38 and 38', one of said channels 38' leading within a hollow piston 53 at 53' and the other, 38, connected at 54' to a channel, 54 around the reduced end of said piston. Seated on the end of said piston is a piston valve 55 extending across the cylinder walls and held in place by a stiif spring 58, this valve being designed on the same principle as that covered in my prior Patent No. 2,069,214, dated February 2, 1937, for Safety device for airplane pilots. Therefore, whenever the pressure in either side of the line rises above a predetermined value, the valve opens and allows the oil to bypass from one side of the line to the other, thus permitting direct manual control and avoiding the locking of the system.

From the foregoing, the operation of my invention will be readily apparent. Persisting excess tension of either cable 8 or I will cause readjustment of the trim tab by the proper actuation of the servo motor 2| from the control valve 8 or 8', which is moved by the tension in the cable. In case both cables 6 and I are placed under continuing tension, both valves 8 and 8' would be lifted, which will not drive the motor 2| in either direction, but will permit ready manual adjustment through hand wheel 5', since under those circumstances the oil is bypassed through the two valves 8 and 8', which are both open. In case of failure or faulty operation of the servo motor, it may be either bypassed manually by turning crank 46, or else over-controlled from handwheel 5 either by reason of the safety valve 55 or by reason of both valves 8 and 8' being open at the time.

a As many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

Having described my invention, what I claim and desire to secure by Letters Patent is:

1. In a control device for aircraft, the combination with a main and an auxiliary or trim control surface, primary means for moving said main surface, auxiliary servo-motive means for moving said trim surface, and means responsive to an unbalanced force acting between said main surface and its actuating means for causing actuation of said servo means to readjust said trim surface to eliminate said force.

2. A control device for aircraft as claimed in claim 1, in which said primary means is connected to said main surface through cables, the relative tension of which constitutes the motivating unbalanced force causing actuation of said servo means to readjust the trim surface.

3. .In a control device for aircraft, the combination with a main and an auxiliary or trim control surface, primary means for moving said main surface, auxiliary servo-motive means for moving said trim surface, strain members connecting said surface and said means, and means responsive to an unbalanced strain in said members for causing actuation of said servo means to readjust said trim surface to eliminate said strain.

4. In a control device for aircraft, the combination with a service and an auxiliary trim rudder and a controller for the former, means for connecting the controller and said service rudder to steer the craft, a servo motor for operating the trim rudder, and means responsive to continuing unbalanced pressure from said service rudder on said connecting means for controlling said servo motor to readjust the latter to relieve said pressure.

5. In a control device for aircraft, the com bination with a service and an auxiliary trim rudder and a controller for the former, means for connecting the controller and said service rudder to steer the craft, a servo. motor for op- 10 main surface, auxiliary hydraulic servos-motive means for moving said trim surface, a cable connecting said primary means and main surface, and means connected to said cable responsive to increaseof tension therein for supplying fluid under pressure to operate said servo motor. 7 An automatic trim regulator as claimed in claim 6, having an adjustable speed valve in the fluid pressure line to regulate the rate of movement of the trim surface.

- BERT G. CARLSON. m 

